Tuning means for reflex klystrons



July 15, 1958 R. c. HERGENROTHER 2,843,794

TUNING MEANS FOR REFLEX KLYsTRoNs Filed oct. 14, 1954 2 sheet-sheet 1Filed Oct. 14, 1954 July 15, 195s RQ C. HEGENROTHER 2,843,794

TUNING MEANS FOR REFLEX KLYSTRONS 2 Sheets-Sheet 2 /N VEN T01? PUDOLF C.MERGE/women Byffw-w A TTolPNL-V 2,843,794 Patented July 15, 1958 TUNINGlVIEANS FOR REFLEX KLYSTRONS Rudolf C. Hergenrother, West Newton, Mass.,assignor to Raytheon Manufacturing Company, Waltham, Mass., acorporation of Delaware Application October 14, 1954, Serial No. 462,353

4 Claims. (Cl. 315-5.22)

This invention relates to rapid mechanical tuning structures for rellexklystrons.

In some applications of radio frequency local osciland the anode blockthat provides a short circuit at the operating frequency while keepingthe plunger free to move relative to the anode block. The radiofrequency short is provided to prevent leakage of the energy past theplunger. This non-contacting short circuit can best be designed asdescribed in an article entitled Broad band non-contacting shortcircuits for co- -axial lines, by William H. Huggins in the Proceedingsof the I. R. E. for September 1947, at page 906i. A grid 25 is mountedacross the bottom of an axial openl ing 26 in the plunger 20. A repellerelectrode 27 is lators, such as in a search radar receiver, it isdesirable to tune the oscillator over its entire usable frequency rangein a short time interval. The conventional internal-cavity reflexklystron can be tuned over a relatively small part of its tuning rangeby means of its repeller voltage but a major change in frequencyrequires a change in the eiective cavity size.V This is accomplished bya mechanical tuning mechanism. Usually this tuning mechanism produces anelastic deformation of some component part of the cavity, and the tubeis severely limited as to the speed of the tuning operation and thetotal number of tuning oper-ations which can he performed before theelastic fatigue causes mechanical failure.

This invention provides a tuning mechanism for an internal-cavity rellexklystron that permits the tube to be operated for more than 100,000,000tuning cycles at speeds as high as 60 complete sweeps of the entiretuning frequency r-ange in one second. This is accomplished by the useof capacity tuning across an adjustable interaction-gap spacing. Thisgap spacing is made adjustable by forming the roof of the cavity as anon-contacting short-circuiting piston that carries the secondinteraction-gap grid and the repeller. The piston is sufticiently broad`band to cover the required tuning range.

Other and further objects and advantages of the invention will beapparent as the description thereof progresses, reference being had tothe accompanying dr-awings wherein:

Fig. 1 lis a sectional view of a klystron constructed according to theinvention;

Fig. 2 is an enlarged view of the tuning structure shown in Fig. l; and

Fig. 3 is a section taken along the line 3--3 of Fig. 1.

in Fig. l the reference numeral 10 designates the anode block formedfrom a piece of conductive material such, as copper, to which isattached a base 11, shown broken away, through which the differentelectrodes are connected to the outer circuit. A cathode sleeve 12 ismounted in a disc 13 that is insulatedly mounted on the anode block 10by means of a dielectric disc 14. The cathode is formed with an inwardlycurved spherical surface 15 which carries the emissive coating 16. Ailament 17 is mounted within the cathode sleeve 12 to provide thenecessary heat. The anode proper is in the form of a irst grid 18 withthe center portion bent upward away from the cathode 15. A plunger 20 ismounted within an opening 21 in the anode block 10 and is supported by aspring assembly 22 in such a manner that it may be moved axially withinthe opening without touching the walls of the opening 21. The lower end24 of the plunger 20 is formed of two pieces so shaped as to provide abroad band non-contacting short circuit for the coaxial transmissionline formed by the plunger 20 mounted within the opening 26 andinsulated from the plunger 20 by a dielectric sleeve 28. The repellerelectrode is preferably formed with a cup 30 at its lower end. Therepeller is connected to a source of potential by means of a conductor31 passing through an insulating bushing 31a in the plunger 20.

The construction ofthe plunger 20 and the repeller 27 are best seen inFig. 2. The manner in which the plunger 20 is mounted on the anode block10 by means of the spring assembly 22 is best seen in Fig. 3. Theplunger 20 is brought out to the outside through a bushing 32 and isattached to a sylphon bellows 33 by means of a collar 33a. The bellowsis in turn attached to the cylindrical housing 34 of the spring assembly22. This housing is in turn attached to the anode `block 10 by means ofa series of vacuum tight seals formed in any of the well-known ways. Theplunger20 is driven axially by a coil 35 attached to its upper end andmounted in the field of a magnet 36. The coil 35 is supplied with analternating current at the desired modulating frequency which mayconveniently be cycles per second from a source 37. The driving meansshown is intended to operate like that of a loud speaker. However, anyconvenient means for producing a reciprocating axial motion of theplunger may be used. The output of the klystron oscillator is mostvconveniently obtained through a wedge-shaped opening 38 in the anodeblock 10 with the apex of the wedgeshaped opening 38 at the spacebetween the grids 18 and 25. This opening 38 is sealed hermetically by aglass window 40 in an iris 41 formed in a metallic cap 42. A groove 43is formed in the anode block 10 about the openingl 38 and so dimensionedas to Vform a choke at the operating frequency of the oscillator so thata wave guide may be attached to the iris to transmit the oscillatoroutput to other equipment where it may be used.

The spring assembly 22 shown in Fig. 3 is composed of a series ofS-shaped springs 44 attached at their midportion to the plunger 20 bymeans of rings 45 and at their outer ends to a cylindrical shell 46 bymeans of rings 47. This mounting structure is designed as an elasticsystem having a high compliance along the axis of the tube and Va lowcompliance in the perpendicular direction. The elastic limit should, ofcourse, exceed the expected displacement of the plunger which, in arepresentative case, is of the order of one thousandths of an inch. Theresonant frequency of the structure should exceed the expected highestmodulation rate. As the springs 44 form part of the heat conduction pathfrom the second grid to the anode block, the total crosssectional areaof the springs should be as large as required to transmit the expectedheat. However, the crosssectional area of a single spring also affectsthe compliance of the spring. The two factors can he balanced todisspate the required heat through a spring structure of the requiredcompliance.

This invention is not limited to the particular details of construction,materials and processes described, as many equivalents will suggestthemselves to those skilled in the art. It is accordingly desired thatthe appended claims be given a broad interpretation commensurate withthe scope of the invention within the art.

What is claimed is:

1. A mechanically tunable klystron oscillator comprising a cathode, ananode, first and second grids, a reflector, a plunger movably mounted inan opening in said anode, the inner end of said plunger being formedwith a cavity' opening tothe outer surface of the plunger and sodiminished as to form a non-contacting short across the opening in theanode, said reflector being insulatedly mounted on said plunger, saidsecond grid beingV mounted on said plunger, and means for causing axialmovement of said plunger so as to move the second grid with respect tothe trst grid to vary the operating frequency. i 2. A mechanicallytunable klystron oscillator comprising a cathode,4 and anode, iirst andsecond grids, a reflector, a plunger movably mounted in an opening insaid anode, the inner end of said plunger being formed with a cavityopening to the outer surface of the plunger and so diminished as to forma non-contacting short across the opening in the anode, said reflectorbeing insulatedly mounted on said plunger, said second grid beingmounted on said plunger, and means for causing axial movement of saidplunger so as to move the second grid with respect to the first grid tovary the operating frequency comprising a coil attached to said plungerand mounted within the field of a magnet and supplied with alternatingeurent.

3. A mechanically tunable klystron oscillator comprising a cathode, andanode, iirst and second grids, a

reflector, a plunger movably mounted in an opening in said anode bymeans of at least one S-shaped spring, the inner end of said plungerbeing formed with a cavity opening to the outer surface of the plungerand so diminished as to form a non-contacting short across the openingin the anode, said reector being insulatedly mounted on said plunger,said second grid being mounted on said plunger, and means for causingaxial movement of said plunger so as to move the second gridfwithrespect to the irst grid to vary the operating frequency.

4. A mechanically tunable klystron oscillator comprising a cathode, ananode, first and second grids, a reflector, a plunger movably mounted inan opening in said anode by means of at least one S-shaped spring, theinner end of said plunger being constructed to form a non-contactingshort with said opening, said reflector being insulatedly mounted onsaid plunger, said second grid being mounted on said plunger, and meansfor causing axial movement of said plunger so as to move the second gridwith respect to the irst grid to vary the operating frequency comprisinga coil attached to said plunger and mounted within the iield of a magnetand supplied With alternating current.

References` Cited in the iile of this patent UNITED STATES PATENTS2,419,121 Clilord Apr. 15, 1947 2,429,243 Snow et al. Oct. 21, 19472,513,277 Best July 4, 1950 2,651,738 Ebers Sept. 8, 1953

